Ответ:

[tex](2x + \frac{1}{x} ) ^{2} = 4 {x}^{2} + \frac{1}{{x}^{2} } + 4[/tex]

[tex](2x + \frac{1}{x} ) ^{2} = {7}^{2} = 49[/tex]

[tex]4 {x}^{2} + \frac{1}{{x}^{2} } + 4 = 49[/tex]

[tex] 4 {x}^{2} + \frac{1}{{x}^{2} } = 45[/tex]